Propeller for aircraft and the like



May 30, 1939. R. L. LEVY PBOPELLER FOR AIRCRAFT AND'THE LIKE Filed May 16. 1935 Patented May 30, 1939 PATENT OFFICE PROPELLER- FOR AIRCRAFT AND THE LIKE Ren Lucien Lvy, Montrouge, France, assignor to Socit d Inventions Aeronautiques et Mecaniques S. I. A. M., Fribourg, Switzerland Application May 16, 1935, Serial No. 21,856

' In France June 5, 1934 a 3 Claims.

This invention relates to improvements in devices for regulating the pitch of propeller blades. The invention pertains more particularly to actuating systems for controlling the blades of var iable pitch propellers, in which the variable aerodynamic pressure exerted on the blades as the latter rotate about the axis of the drive shaft, is continuously and automatically balanced by a back pressure furnished by a device whichfunctions oleopneumatically.

The primary object is to improve devices of this general character by providing a propeller wherein the hub of said propeller is rotatably mounted onthe drive shaft or an intermediate hub and is driven through an oleopneumatic coupling arranged between said propeller hub and said intermediate hub, which coupling yields in response to the torque transmitted to the propeller hubthrough said coupling. The relative rotary movement of the propeller hub and intermediate hub, acting through suitable devices to adjust the pitch of the blades in accordance with the relative rotary displacement thereof.

With the above and other objects in view'which will appear as the description proceeds, the invention consists in the novel features hereinafter described in detail, illustrated in the accompanying drawing and more particularly pointed out in the appended claims. t

In the drawing,

Fig. 1 is a front elevation, partly in section, of 5 ""Figfiii is a fragfnentaq detail inside elevation of a further modificationw Referring to the drawing in detail,- P designates a pair of propeller blades rotatably mounted in a common blade carrier or hub A. The blades are adaptedto rotate in said hub on the vertical axis X-Y, which axis also extends through the,

centres C of aerodynamic thrust exerted on the blades, as-shown in Fig. 3. The hub A is rotatably mounted on an intermediate hub or member B which is keyed or otherwise secured to the front end of the main drive shaft M. The hub A will, of course, rotate about the axis 241 of the drive shaft M. H h

An oleo-pneumatic "coupling H, preferably formed integral with the intermediate hub B,

transmit the torque of the intermediate hub to and each piston is connectedto its respective propeller hub by means of a rod n, slidably engaging a bolt K projectinglaterally from said hub.

When the engine is running and the drive shaft rotating in the direction of the arrow f (Fig. 3), the intermediate hub B will drive the propeller hub A through the agency of the oleo-pneumati'c coupling. However, due to the aero-dynamic pressure exerted against the blades, the latter appear to turn through an angle a (off-set position, X Y of the axis X-Y), in the retrograde direction .f', until the air pressure in the cylinders H of the oleo-pneumatic coupling balances the. aero-dynamic pressure exerted on the .centres of the thrust C on the blades.

In assuming this angle of lag 0: around the main axis Z-T, the intermediate hub B causes the blades P to turn on their longitudinal axis XY. To accomplish this purpose, the inner end 1) of each blade is' provided with a finger g which extends through an opening Zin the propeller hub A and engages a fork t carried by the intermediate hub B. The action of the forks t on the fingers g varies the turning of the blades on their longitudinal axis X-Y in a direction which corresponds with a reduction in the pitch of the propellers. Consequently, by this reduction in the pitch of the propellers, the aerodynamic thrust exerted against the blades and its effect upon the main drive shaft M is decreased. The speed of the engine increases therefore, until'the aerodynamic pressure against the blades is'balplane be small, the angle a will be of maximum value and consequently the pitch of the propeller will ata minimum. If said couple be still large,

tlcularly' indicated.

density vary simultaneously, the angle a and,.-

consequently the movement of the blades about their axis X- -Y, will vary at the same time until the position of equilibrium is attained, which ensures the optimum value of propeller pitch compatible with the new rlmning conditions.

A ,variable pitch propeller possessingjthe two fundamental characteristics defined above, therefore enables the pitch to adapt itself automatically in the most suitable manner, whatever may be the running conditions, speed or altitudes at which the aeroplane is flying. Its application to engines fitted with superchargers appears par- While other elastic couplings may be employed between the intermediate hub and the propeller hub, it will bepoted that the oleo-pneumatic cylinder coupling herein defined oflers several important advantages.

In the first place, this coupling-affords the possibility of acting upon the variables, namely, the initial pressure of the air, and the clearance in the cylinders for the compressed air.

The propeller being adjusted to maximum pitch, the air pressure in the cylinders of the coupling H is adjusted initially so that the propeller wfll j assume, atthedetermined point, the minimum pitch that is desired. If desired, suitable means (not shown) may-be provided to permit the pilot to admit oil into the cylinders during flight when the engine races, in order to reduce the clearance in said cylinders while maintaining the same initial pressure of inflation.

Another 'advantage'ofthe present type of coupling' is that the, ole'o-pneumatic cylinders ensure hydraulic damping of the; vibrations and shocks to' which the propeller may be exposed as.

the result of changes in speed. To accomplish this result, I provide a diaphragm J in each cylinder, provided with a relatively small bore 1 which damps the, movement of the pistons I in a well known manner.

Furthermore, oleo-pneumatic couplings of this type enable the pitchof the propeller to adjust itself automaticallyto the altitude. For xample, as theaeroplaneascends, the compressed air in the cylinders-of the coupling H retains its initial pressure; whereasthe aerodynamic remaybe exposed during the operation of the aeroplane, I prefer to employ the 'spaceein the rear of the pistons I as a dashpot, to'prevent shoclrs in the event of a more or less sudden drop in the enginespeed:v In such case, the piston rod passing through a stumng box i, is articulated on the member K by. means of a slot n or other connecting means allowing similar freedom of-move ment. The space e isconnected with a casing 20 by a pipe II. Thehead of the cylinder 11 is provided with a small bleed passage '23. A check valve 22 is provided in the casing adjacent the outlet end ofthe pipe II to permit the airfrom the space e to pass on out through the casing, but preventing the return chair to the space e through said casing.

It should also be mentioned that the inner end p of the blades P may be connected with the intermediate hub B by means other than the finger a, and fork t described, above. Forexample, .as shown in Fig. 6, two bevel pinior'is, one of which (I 5) is integral with the inner end .of v the blade P, and the other (I5) integral with the plish the same purpose, that is, of the propeller. It will be understood vary the pitch that the system of automatic adjustment just described can be applied fintermediate hub B may be employed to accomm to any propulsive device for aeroplanes or the like, having a variable-pitch propeller.

The invention also comprises a simple device 'for assuring the continuous lubrication of the ing through the hub of the propeller. Whatever system may be employed, it is essential to insure thorough lubrication of the contact surfaces,

in order that under the action of the efforts to which i it is subjected, the propeller may assume the pitch corresponding'with the optimum output of the o propulsive system.

According to the present invention, a particularly advantageous methodof lubrication consists in utilizing the action of centrifugal force to produce anfeflective forced lubrication of the inclinesor sliding surfaces. In an embodiment represented in Fig. 5, where the blades turn on a heiicbidalramp, a cylinder housed in the inner" end 5 ofthe blades P and preferably coaxial with the rotational axis X-Y of the blade 40 contains a pistdn 2, which is provided with a skirt or cup 3 and is continuously subjected to v the ,action of a spring 4 tending to press it radially inwards. This piston 2 is composed of a of a lead heavy metal, for example, in'the form block.

The upper compartment [of the cylinder I, communicates, through es 6, with various points on thehelicoidal ramp 1, and may also communicate with the various members of thehub' that are to be lubricated, especially the fingers actuating the movement of the blades:

-When the propelleris a rest, oil is injected through a suitable passage 8, into the center of propeller hub, a resilient cou'pling including pneumatic cylinders rigid with one of said hubs,

and piston members arranged in said cylinders and connected to the other hub for transmitting therotary motion of the driving shaft to said propeller blades, said resilient coupling respond-- 1 me during rotation of said shaft whereby an an- Eula! displacement-occurs between the propeller "I hub and; said shaft, means connecting said intermediate hub with said blades for varying the pitch of said blades a definite relative value for each value of said angular displacement, and diaphragms in said cylinders having openings for retarding the movement of fluid in said cylinders.

2. In a propelling mechanism, a driving shaft, an intermediate hub fixed to said shaft, a propeller hub, rotatably mounted on said intermediate hub, propeller blades 'rotatably mounted in said propeller hub, a resilient coupling including pneumatic cylinders rigid with one ofsaid hubs, and piston members arranged in said cylinders and connected to the other hub fortransmitting the rotary. motion of the driving shaft to 'said' for each value of said angular displacement, and

means in said cylinders for restricting the movementof fluid therethrough.

3. In a propelling mechanism, a driving shaft, an intermediate hub fl'xed to said shaft, a propeller hub rotatably mounted on said intermediate hub, propeller blades rotatably mounted in said propeller hu-b, aresilient coupling including pneumatic cylinders rigid with one of said hubs, and piston members arranged in said cylinders and connected .tothe other hub for transmitting the rotary motion of the'driving shaft to said propeller blades, said resilient coupling responding during rotation of said shaft whereby an angular displacement occurs between the propeller hub and said shaft, means connecting said tation of the driving shaft.

RENE LUCIEN LEVY. 

